Bosonic qubit encodings are two-dimensional subspaces within the infinite-dimensional Hilbert space of a bosonic mode.
Good choices of this two-dimensional subspace allow for experimentally convenient ways of preparing the encoded qubit states, implementing desired unitary gates, and faithfully performing measurement readout.
In some cases, the redundancy of the full infinite-dimensional Hilbert space can even be leveraged to detect and correct CV errors – random Gaussian displacements, rotations, and photon loss, for a few – without destroying the encoded information.
Examples of bosonic codes include GKP [1]}, dual-rail [2]}, [3]}, cat [4]}, [5]}, hypercat [6]}, [7]}, binomial [8]}, and general rotation-symmetric codes [9]}.
